Backport fix for GCC bug 117811

[benoit-pierre]

Cf. koreader/koreader#12805 & https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117811.

Patch: https://gcc.gnu.org/cgit/gcc/commit/?id=7679b826840c58343d72d05922355b646db4bdcc

[NiLuJe]

Should be easy to add to the ct-ng patchset, I'll see if I can find some time to do it in the next few weeks, thanks for the heads up ;).

[benoit-pierre]

Fixed with #56.